1. Field of the Invention
The present invention relates to an applicator, assembly, and method for connecting an inlet conduit to a hollow organ, and more particularly, to a hemostatic connection assembly and inlet conduit connectable to the apex of a heart.
2. Description of the Related Art
As the average age of the United States population increases, so do the instances of aortic stenosis. An alternative approach to the conventional surgical replacement of the stenotic aortic valve involves the use of an apicoaortic conduit. In this approach, the native aortic valve is not removed, and a prosthetic valve is implanted in a parallel flow arrangement. A connection conduit (or tube) connects the apex of the heart to the descending aorta. Somewhere along this conduit, the prosthetic valve is interposed. Thus, blood leaves the heart through the apex and travels through the conduit (with valve) to the descending aorta.
Until recently, surgical procedures to implant an apicoaortic conduit have included a single, long incision, such as in the 6th intercostal space, to expose the heart and allow retraction of the lungs to expose the descending aorta. Recognizing the potential for broader scale use of the apicoaortic conduit for aortic valve replacement, some surgeons are now attempting to use smaller incisions and are requesting development of surgical tools for a minimally invasive procedure.
A typical implantation procedure for an apicoaortic conduit is described as follows. The patient placed is on the operating table in the supine position. Anesthesia is induced, and the patient is intubated with a double-lumen endotracheal tube, which facilitates one-lung ventilation and allows the surgeon to work within the left chest. The patient is positioned with the left side up (90 degrees). The pelvis is rotated about 45 degrees, such that the femoral vessels are accessible. An incision is made over the femoral vessels, and the common femoral artery and vein are dissected out. Heparin is administered. Purse string sutures are placed in the femoral artery and vein. The artery is cannulated first, needle is inserted into the artery, and a guide wire is then inserted. Transesophageal echo is used to ascertain that the wire is in the descending aorta. Once this is confirmed, an arterial cannula is inserted over the wire, into the artery using the Seldinger technique (Sven-Ivar Seldinger: Catheter replacement of the needle in percutaneous arteriography (a new technique) Acta Radiologica, Stockholm, 1953, 39:368-376). The arterial cannula is typically 19 or 21 French. Once inserted, the purse string sutures are snugged down over tourniquets. A similar procedure is followed for the femoral vein. The venous cannula is usually a few French larger than the arterial cannula. Once both vein and artery are cannulated, the cannulae are connected to the cardiopulmonary bypass, and the capability to initiate cardiopulmonary bypass at any time is present.
A 1 cm incision is made in approximately the 7th interspace in the posterior axillary line, a videoscope (10 mm diameter) is inserted, and the left chest contents viewed. The location of the apex of the heart is determined, and the light from the scope used to transilluminate the chest wall, which this allows precise localization of the incision. The incision is then performed, which is essentially an anterior thoracotomy, typically in the 6th interspace. Recent incisions have been about 10 cm long, but are expected to become smaller and smaller with time. A retractor is inserted and the wound opened gently. A lung retractor is used to move the (deflated) left lung cephalad. A pledgeted suture is placed on the dome of the diaphragm and positioned to pull the diaphragm toward the feet (out of the way). The pericardium is incised about the apex of the heart, and the apex is freed up and clearly identified.
Currently available commercial devices used to construct the implantable apicoaortic conduit include the Hancock valved conduit and Hancock apical connector (from Medtronic, Inc. 710 Medtronic Parkway, Minneapolis, Minn., 55432-5604 United States), which are sewn together to form the complete implant assembly. The assembly is brought to the field, and a measurement made from the apex of the heart to the descending aorta. The assembly is trimmed appropriately. A partial-occluding clamp is then placed on the descending aorta, and the aorta opened with a knife and scissors. The outflow end of the conduit is then sutured to the descending aorta using 4-0 prolene suture, in a running fashion. Once this is complete, the clamp is removed and the anastomosis checked for hemostasis. Blood is contained by the presence of the Hancock valve.
The most technically challenging aspect of implanting the apicoaortic conduit is placement of the apical connector, which has historically been performed in a two-step process by first cutting and removing a cylindrical tissue plug from the apex and then inserting the apical connector into the formed hole. This two-step process creates potential for significant blood loss after the hole is formed and before the apical connector is inserted. Placement of the apical connector has historically been performed as follows. The apical connector is placed on the apex, and a marker is used to trace the circular outline of the connector on the apex, in the planned location of insertion. Four large pledgeted sutures (mattress sutures) of 2-0 prolene are placed, one in each quadrant surrounding the marked circle. The sutures are then brought through the sewing ring of the apical connector. A stab wound is made in the apex in the center of the circle, and a tonsil clamp is used to poke a hole into the ventricle. Cardiopulmonary bypass is typically initiated at this point. A Foley catheter is inserted into the ventricle, and the balloon expanded. A cork borer is then used to cut out a plug from the apex. The apical connector is then parachuted down into position. A rotary motion is necessary to get the connector to seat in the hole. The four quadrant sutures are tied, and hemostasis is checked. If there is a concern regarding hemostasis, additional sutures are placed. The retractor is removed, chest tubes are placed, and the wound is closed.
An improved alternative method and device for placement of the apical connector is described in U.S. patent application Ser. No. 11/086,577, (U.S. Patent Application Publication No. 20050251187), which is hereby incorporated by reference in its entirety. The '577 application describes an applicator and connector conduit (referred to interchangeably as the apical connector) adapted for cutting and removing a cylindrical tissue plug from the apex while the connector conduit is being inserted into the formed hole. This device allows placement of the connector conduit without cardiopulmonary bypass and with minimal blood loss.
The '577 application discloses an apparatus and method for connecting a first conduit to the heart without the need for cardiopulmonary bypass. The first conduit may then be attached to a second conduit that has a prosthetic device interposed. The second conduit may be connected to the aorta prior to the first conduit being attached to the heart. The prosthetic device may be a prosthetic valve or a pump, for example. The apparatus includes an implantable connector with first conduit component, a retractor expansion component, a coring component, and a pushing component. The retractor expansion component is slide-ably coupled to the coring component. The retractor expansion component serves to seat against and separate the inside apical wall of the left ventricle so that the coring component may cut cleanly through the myocardium to form a tissue plug without leaving any hanging attachments to the inside walls. By remaining seated against the inside wall of the hollow organ, the retractor expansion component follows the tissue plug into the coring component. The surgeon applies force and rotary motion to the pushing component sufficient to cut the tissue plug and implant the prosthetic component.
Prior art FIGS. 1A and 1B are copies of FIGS. 10A and 10B of the '577 application, presented herein for illustrative purposes. As described in the '577 application, hemostasis is achieved during implantation of the conduit by substantially blocking leak paths through and around the connector conduit.
Referring to the figures, the connector conduit has a structural frame 120 defining a rigid portion, which may be constructed from a single material or a combination of materials. The structural frame 120 includes a tapered leading edge 110 designed to reduce the effort needed to push the connector through the heart wall located at one end of a cage section 120 and a bend portion 140 that is normally biased into a bent configuration. During use, cage 120 resides primarily within the heart wall, so it must be constructed so as to be rigid enough to not collapse due to radial forces exerted by the heart wall. The cage 120 may include cage slots 121. The cage slots 121 allow the passage of thread to secure the conduit or the sewing flange. A holder 130 is formed at one end of cage 120 and may be used to grasp the connector during implantation. Holder 130 may have a slot-and-key configuration with the applicator, and may utilize holder slots 431. In a preferred configuration, the holder 130 relies upon both a slot-and-key and a tight friction fit to lock the holder 130 relative to the applicator.
Bend portion 140 includes circular rings 141 and a curved spine 142. The circular rings 141 prevent radial collapse of the conduit, and the curved spine 142 holds the conduit in a preferred shape to direct blood flow from the heart to the aorta. The curved spine 142 may be at the outer radius of bend portion 140 (as shown) or at the inner radius of the flexible bend. As an alternative, flexible bend 140 may include two curved spines at the mean radius. As another alternative, the structural frame 120 could include circular rings 141 without curved spine 142. As another alternative, a modified coil spring in the shape of a preferred bend could be used instead of circular rings 141 and curved spine 142. Properties of the coil spring would be chosen to prevent radial collapse and to provide appropriate stiffness of the curved position.
As is described in the '577 application, the leak path through the lumen of the connector conduit is substantially blocked by the applicator. The leak path around the connector conduit is substantially blocked by a tight interference fit between the outer surface of the fabric-covered cage 120 and the cut surface of the hole in the apex. This interference fit is the result of the cutting element of the applicator having a smaller diameter than the outer surface of the fabric-covered cage 120. For example, the outer diameter of the cutting element could be 0.7 in and the outer diameter of the fabric-covered cage could be 0.9 in.
Once the connector conduit is implanted and the applicator is removed, the leak path around the connector conduit is blocked to achieve hemostasis in two ways. First, the interference fit remains intact. Second, a sealing surface is formed by tightly suturing the sewing flange to the apex. These sutures also prevent the connector conduit from being pushed out of the hole by the blood pressure in the left ventricle.
Apical connectors consisting of an inlet cannula and sewing cuff are currently used in other applications, such as left ventricular assist devices. For example, Ventricular Assist Devices, referred to as VADs or LVADs, are enclosed pump devices used to augment the pumping capability of a damaged or failing heart. Such devices often have an inlet cannula pre-attached to the body of the device and thus, cannot be preloaded onto the applicator described in the '577 application.
An example of an existing inlet cannula is the Thoratec HeartMate II LVAD's inlet cannulae (Thoratec Corporation, 6101 Stoneridge Drive, Pleasanton, Calif. 94588) which, with the patients on cardiopulmonary bypass, are currently implanted as described as follows. A trocar (or cutting element) is used to cut a hole in the apex of the heart. Several sutures are then placed through the sewing ring of the sewing cuff and through the apex. After the sutures are pulled tight and knots are tied, the sewing cuff is positioned in place. The inlet extension of the inlet cannula is inserted through the sewing cuff and through the hole in the apex until the inlet extension is at the desired position. The position of the inlet extension within the sewing cuff is set and hemostasis is achieved by tightly tying the long suture around the flexible tube of the sewing cuff.
As discussed above, the '577 application describes the insertion of a connector conduit into a hollow organ. Referring again to prior art FIGS. 1A and 1B, as well as prior art FIG. 2, which is a copy of FIG. 14 of the '577 application, the connector conduit includes a cage of structural frame 120 and sewing flange 170. The cage and sewing flange 170 are rigidly connected by a fabric covering. The connector conduit described in the '577 application may be used instead of the inlet cannula on such medical devices as LVADs. The fabric-covered cage is analogous to an LVAD inlet cannula and sewing flange 170 is analogous to an LVAD sewing ring. It is important to note that the inlet cannula and sewing cuff are rigidly connected (thereby setting position and providing hemostasis) only after a long suture is tied tightly around the flexible tube of the sewing cuff.
More specifically, FIG. 2 shows a cross-section of a connector conduit 100 that includes a rigid portion defined by structural frame 120 with bend portion 140, and a flexible portion defined by conduit 160. The rigid portion also includes outer fabric 161, and sewing flange 170. Orientation marks (not shown) may be included on the conduit 160 or outer fabric 161. Conduit 160 may be a pleated vascular graft constructed of woven Dacron. Outer fabric 161 could be a knitted Dacron fabric material that stretches to accommodate contours of the structural frame 120. Sewing flange 170 could be constructed of a soft silicone rubber, for example, to allow easy passage of a needle when fastening sewing flange (or sewing ring) 170 to the outer surface of the heart. To allow visualization on x-ray, for example, the sewing flange could be made radiopaque, such as by mixing barium sulfate into the silicone rubber. The sewing flange may have a cloth covering such as that used for outer fabric 161. Alternatively, the sewing flange 170 may consist entirely of folded cloth. The components of the connector conduit 100 may be fastened together as needed, such as with thread.
U.S. Pat. No. 6,942,672 to Heilman et al. describes an apparatus and method for attaching a conduit to the heart, such as a conduit for connection to an implantable blood pump, or to a blood vessel, as in a heart bypass graft, without the need for a cardiopulmonary bypass. The apparatus can include an enclosure attachable to the heart and having sealed within the enclosure at least part of a coring tool and one end of the conduit which will be attached to the heart. A heart attachment member can be affixed to the enclosure for facilitating attachment of the apparatus to the heart and the coring tool can have a cutting member and a member for holding the tissue to be cut from the heart. All air can be evacuated from the enclosure prior to cutting tissue from the heart and attachment of the conduit.
However, with a system such as that disclosed in the '672 patent, a major difficulty is that, during use, the moment that the coring means penetrates the heart wall, the action of the heart will cause blood to enter the enclosure and either fills it if it is evacuated or mixes with the saline if it is prefilled. In either case, the opacity of the blood or blood saline mixture will obscure further action of the coring means and make accurate placement of the conduit difficult. In addition, because the heart is beating the flexible enclosure will be in constant pulsatile motion further complicating accurate use of the enclosed tools. From the description and the figures in the patent, the enclosure needs to be somewhat large to accommodate the proper movement of the tools and therefore will contain a large amount of blood or blood and saline mixture. If the enclosure is accidentally breached, for example by a sharp edge of the coring tool or the implant, a large amount blood immediately floods the operating field. Since no other means beyond the enclosure is provided to limit flow of blood, the beating heart will pump out a significant additional amount of blood before the field is cleared and the bleeding is controlled. This could result in significantly negative outcomes, including death, for the patient.